Positional information providing system and apparatus

ABSTRACT

When information regarding position of a facility, such as a parking lot, is requested from a terminal ( 22 ), an information center ( 10 ) supplies position information to the terminal ( 22 ) as a relative position using a landmark, such as a neighboring road. The terminal ( 22 ) computes a shift from a position of a landmark in a local map database ( 24 ) and a position of a received landmark in a map matching processor ( 34 ), and corrects the facility position. If the landmark has not been stored in the map database ( 24 ) at the terminal ( 22 ), relative data based on another road is resent.

TECHNICAL FIELD

The present invention relates to a system for transmitting desiredinformation to a terminal from an information center in response to arequest from the terminal, and more particularly to a facilityinformation provider system for providing information regarding acertain facility.

The present invention further relates to a position information providersystem and a position information provider apparatus for recognizingabsolute positions as position data relative to roads.

BACKGROUND ART

Heretofore, navigation apparatuses are known as apparatuses for routeguidance in vehicles. These navigation devices basically function bycontinuously detecting a present position and displaying it on a map.They contain a GPS (global positioning system) apparatus for detectingthe present position and a map database for storing map data.Furthermore, by entering a destination, the navigation apparatussearches for an optimum route from the present position and also guidesthe vehicle in a set travel route in the direction of movement at branchpoints.

Systems have also been proposed for connecting a mobile terminal, suchas in a vehicle, with an information center, and obtaining informationnecessary in the vehicle. According to this type of system, restaurantinformation, sightseeing information, locations of usable parking lots,route guidance services to destinations, and so forth can be obtained asneeded at the vehicle. The positions of and routes to restaurants,sightseeing spots, parking lots, and so forth can also be displayed onmaps.

For example, a system is disclosed in Japanese Patent Laid-OpenPublication No. Hei 7-72234 in which position information of a parkinglot is returned as latitude and longitude data from an informationcenter when information regarding the parking lot is requested from aterminal carried in a vehicle, and the position of the parking lot isdisplayed on a map contained in the terminal.

However, according to the apparatus of this publication, there is aproblem where the displayed parking lot position based on the receivedlatitude and longitude data is not a proper position on the map sincethe map contained in the terminal includes error. Namely, the originmaterial differs in creating the map or a certain amount of error isgenerated among a plurality of maps having different creation methods orprecision. For this reason, a positional relationship with theperipheral condition (such as peripheral roads) of one point specifiedon one map may differ from a positional relationship with peripheralroads of the corresponding point on another map.

For example, even when a point specified by latitude and longitude ispositioned on the right side of a road on one map, a situation may arisewhere it is indicated on the left side of the road on another map.Therefore, a situation may arise where the positional relationship withthe peripheral roads may be incorrectly recognized at the vehicle, suchas for a position of a parking lot specified by the information center.

To prevent this phenomenon, a method has been considered for specifyinga point with respect to a map by a relative positional relationship withrespect to roads (links). For example, this method (tentatively referredto as a relative positioning method) specifies a link by a link number,specifies the distance on the link from the starting point, and furtherspecifies the direction and distance from the starting point. In thismanner, by specifying the point as a relative positional relationship,breakdowns in the positional relationship of the road and the point tobe specified can be prevented. Note that the links are organized inunits of roads separated by intersections, and the road network isexpressed as connections of these links in the map database.

The relative positioning method herein assumes that the link numbers atthe vehicle and at the information center have identical definitions.However, due to differences in source materials and update times, thereare instances where a link specified at the side executing a commanddoes not exist. Furthermore, when there are differences in mapprecision, a link specified at the information center may not exist atthe vehicle. In this instance, a problem is that it might not bepossible to specify a point at the receiving side.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a positioninformation provider system capable of displaying the position (specificposition), such as of a facility for which information was requested, atan appropriate position on a map.

The present invention uses landmarks, such as of road networks, on mapdisplays that are common to the map database of the information centerand to the map database of the terminal so as to correct displacementsbetween the two map databases. The specific position (facility position)to be the information provided is set as a relative position with alandmark on the above-mentioned map in the map database of theinformation center, and correcting the displacement as described aboveenables the above-mentioned specific position to be displayed on the mapat the terminal with the same positional relationship as on the map atthe information center.

Therefore, when the relative position of the above-mentioned landmarkand the above-mentioned specific position is displayed on the map at theterminal, an improper display can be prevented.

For example, if the above-mentioned landmark is a road and theabove-mentioned specific position (facility) is on the right side of theroad according to the map at the information center, the display of thefacility on the map at the terminal on the opposite side, or on the leftside of the road, can be prevented. Therefore, a problem can beprevented in which a facility, thought by the driver to be on the leftside of the road on the map, appears on the right side. In the relativeposition with the above-mentioned landmark, problems arise, such as theabove-mentioned facility being incorrectly displayed on the oppositeside of the road, and besides the above-mentioned road, a railroadtrack, a river, a coastline, and so forth are landmarks. In the case ofa river, which can be crossed only at a bridge, if a facility isdisplayed on the opposite side of its actual position and thedestination is incorrect, the bridge must be crossed in order to returnto the correct position and much time will be wasted. A similarsituation occurs for a railroad track. In the case of a coastline, thereis the possibility of having an unnatural display in which the facilityto be the destination is shown in the middle of the ocean. Extractingfrom the landmarks on the map display can prevent such improper displaysdescribed above.

Furthermore, the information regarding the above-mentioned landmark canbe made to include the shape and type of the relevant landmark. Anexample of landmark type for roads is the route number or name tospecify a road, such as national route 1 or Keihin route 3. On the basisof information on type, the number of landmarks to be searched by shapecan be reduced and processing in a short time becomes possible.

Furthermore, the above-mentioned terminal transmits the type of mapdatabase held in the relevant terminal, and the above-mentioned positioninformation generating means extracts the above-mentioned landmark inaccordance with the received type of map database and generates positioninformation.

According to this configuration, from the information stored in the mapdatabase held in the terminal, such as that indicating the degree ofdetail of the map, the information center can provide informationregarding the facility on the basis of map information according to thedegree of detail of this map. For example, if the roads stored in themap database of the terminal are only highways, the information centerextracts from the map database the highway found in the periphery of thefacility as the peripheral landmark, and if local roads, such asmunicipal roads, are also stored in the terminal, the information centerextracts from these roads the roads in the periphery of the facility andsends them to the terminal. Therefore, the information that can beeffectively used at the terminal can be transmitted from the informationcenter.

Furthermore, in the above-mentioned information provider system, whichtransmits the type of map database held in the terminal to theinformation center, the peripheral landmarks that the above-mentionedposition information generating means extracts include roads accordingto the above-mentioned received type of map database held in theterminal, and the information regarding a specific position can be madeto include a reference point, which has been set in advance on theabove-mentioned extracted road, and detailed route information up to thespecific position to be provided.

According to this configuration, sending route information from theabove-mentioned reference point to the above-mentioned specific position(facility) enables a map to be sent with more detail than the mapdatabase held in the terminal, thus allowing the facility position to bedisplayed in more detail.

Furthermore, in the various above-mentioned information providersystems, the peripheral landmarks that the above-mentioned positioninformation generating means extracts can be two mutually connectedroads positioned to sandwich the specific position (facility) of theinformation to be provided. According to this configuration, the displayaccuracy of the facility of the information to be provided can beimproved.

It is preferable for the information center to generate relativeposition data using links, which are units forming the roads. Theterminal requests a retransmission when the link that is used in thereceived relative position data does not exist in the terminal mapdatabase, and the information center, upon receiving the retransmissionrequest, transforms the absolute position data into relative positiondata with another close link and retransmits it.

Therefore, when the link used in the relative position data in theinformation center does not exist in the map database at the terminal,the information center retransmits the relative position data usinganother link so that the position can be specified in the terminal usinganother link.

Transforming the absolute position data, such as of a facility, intorelative position data enables the regular map database in which theabsolute positions and coordinate positions are associated to be used.

The above-mentioned center map database stores a rank for each link, andit is preferable for the information center to transmit relativeposition data using a link having a rank higher than that of the linkpreviously transmitted during retransmission.

The map database at the terminal often has a low accuracy, and the dataregarding roads having high ranks is often common to the map databases.Using the link having a high rank during retransmission can raise theprobability that the relative position data can be recognized at theterminal.

It is preferable for the above-mentioned information center to alsotransmit the absolute position data during transmission of the relativeposition data, the above-mentioned terminal to specify the link close tothe absolute position data existing in the terminal map database duringa retransmission request, and the above-mentioned information center totransmit the relative position data using the specified link in theretransmission request. In order for the terminal side to specify a linkto be used by the relative position data, the relative position datathat used the link must exist in the map database at the terminal.Therefore, the transmission of reliable position information can beachieved from retransmission.

It is preferable for the information center to transmit data regardingthe shape of the link that did not exist in the terminal map database tothe terminal, and for the terminal to update the terminal map databasefrom the received data regarding the shape of the link. Data regarding anew link is added to the terminal map database in this manner. This newlink is useful in specifying the provided position, and it is preferablyused until the position is reached. This update realizes a morepreferable route guidance for the next driving trip.

It is preferable for the information center to use data on the shape ofthe link to be transmitted as relative data using the link which existsin the terminal map database. With the relative data using the linkwhich exists in the terminal map database in this manner, correctrelative position relationships of new links and already existing linkscan be maintained.

Furthermore, it is preferable to include a map database for storing theroad network as coordinate values on the map associated with absolutepositions, and transforming means for transforming an arbitrary absoluteposition into a relative position with the road network, and to providethe absolute position data after conversion into relative position data.As a result, transactions of position information from relative positiondata are performed using the regular map database.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a first embodiment of a positioninformation provider system concerned with in the present invention.

FIG. 2 is a control flowchart at an information center of the firstembodiment.

FIG. 3 is a control flowchart at a terminal of the first embodiment.

FIGS. 4(a), 4(b), 4(c) and 4(d) illustrate the matching of informationfrom the information center with information of map database of theterminal of the first embodiment.

FIG. 5 is a control flowchart showing an example of a creation method ofperipheral landmark information of the first embodiment.

FIG. 6 is a control flowchart showing an example of a creation method ofperipheral landmark information of the first embodiment.

FIG. 7 illustrates a search range for peripheral landmarks.

FIG. 8 illustrates an example where a detailed map of a facilityperiphery is included in facility position information.

FIG. 9 is a block diagram showing a general configuration of a secondembodiment.

FIG. 10 illustrates contents of relative position data of the secondembodiment.

FIG. 11 shows the organization of relative position data of the secondembodiment.

FIG. 12 shows ranks of roads.

FIG. 13 shows an example of a point and ranks of links adjacent thereto.

FIG. 14 is a flowchart showing an example of a retransmission procedurefor the second embodiment.

FIG. 15 is a flowchart showing another example of a retransmissionprocedure for the second embodiment.

FIG. 16 shows the organization of shape data for a link.

FIG. 17 illustrates correction of a link shape.

MODE(S) FOR CARRYING OUT THE INVENTION

Embodiments of the position information provider system to which thepresent invention concerns are described with reference to the attacheddrawings.

First Embodiment

FIG. 1 shows a simplified configuration of the first embodiment. Aninformation center 10 has a map database 12 for storing informationnecessary to display a map, such as the information on topography ofrivers and coastlines and on structures of roads, bridges, andbuildings. This map database 12 can also store information regarding theabove-mentioned structures, and if the structure is a parking lot, forexample, information on the parking lot's capacity as well as thepresent number of parked cars. The information center 10 has acontroller 14 for reading out information from the map database 12 inaccordance with an information request of a terminal to be describedlater. When there is a request for information regarding a certainfacility from the terminal, the controller 14 has a facility positioninformation generator 18 which extracts from the map database 12 apredetermined number of information items regarding landmarks in linearform on the map notation, such as rivers, railways, and roads in theperiphery of the relevant facility, and furthermore reads outinformation regarding the relative position of the above-mentionedfacility with the peripheral landmarks from the map database 12. Theinformation center 10 has a radio communications unit 20, whichtransmits information regarding the positions of peripheral landmarksand information regarding the positions of facilities and receivesinformation transmission requests from a terminal 22.

Meanwhile, the terminal 22 is disposed in a moving object, such as anautomobile. The terminal 22 also has a map database 24, which need notbe identical to the map database 12 of the information center 10. Mapdatabases have varying degrees of accuracy depending on the manufactureror depending on the specifications even from the same manufacturer, andthe degree of map detail, such as the narrowness of the roads stored,may differ with every database. The terminal 22 further has a radiocommunications unit 26, which requests information on a desired facilityfrom the information center 10 and receives information transmitted fromthe information center 10 according to the request. A controller 28 isprovided for checking the data of the map database 24 held in theterminal with the information regarding a facility received by the radiocommunications unit 26. A display unit 30, such as for displaying mapsaccording to commands from the controller 28, and an operating unit 32,such as for use by a driver in selecting desired information on afacility, are provided. Furthermore, a map matching processor 34 isprovided for calculating the amount of shift between the map databasesof the information center and the terminal by comparingcharacteristically shaped objects on the map display from informationsent from the information center 10 with corresponding landmark shapesin the map database 24 of the terminal.

As mentioned above, map databases have varying degrees of accuracydepending on their type. This is due to the reasons given hereinafter.

One is that maps are planar representations of topography originallyshaped on a sphere so that error is introduced during thistransformation. In maps of a scale used in vehicle route guidanceapparatuses, the transformation from spherical to planar is performedfor every predetermined section, resulting in an increase in errorduring transformations at the periphery of each section. If theprocessing of this error differs with every map database, points withthe same latitude and longitude may be represented differently.Furthermore, if the sections are assigned differently with every mapdatabase, a point near the center of a section in one map database andhaving only a slight error from transformation may be in the peripheryof a section in another map database and have a considerable error fromtransformation. Thus, in this case, the same point is represented asdifferent positions in these two databases.

Next, since the map databases used in automobile route guidanceapparatuses assume that the route guidance is to be performed withcertainty, the positions of roads may be displayed at positionsdifferent from actuality. For example, there are instances where agently curved road actually having a large radius is displayed as astraight road. Also, if an ordinary road runs below and a turnpike runsabove so that the two roads match perfectly and are indistinguishablewhen shown on a map, there are instances where one of the roads ispurposely displayed in a position that is different from actuality. Ifthere is a difference in map notation between map databases,discrepancies in indicated positions may result where a facility shownon the right side of a road in one database is shown on the left side ofthe road in another database.

This embodiment intends to match the information between different mapdatabases in accordance with the method to be described hereinafter.

FIGS. 2 and 3 are flowcharts regarding basic control operations of theapparatus of the present embodiment. In particular, FIG. 2 is aflowchart of processing at the information center and FIG. 3 is aflowchart of processing at the terminal. Furthermore, FIGS. 4(a)-4(d)illustrate the information processing of the apparatus of the presentembodiment.

First, a request for information regarding a certain facility is sentfrom the terminal 22. This control operation is not shown in particularin the flowchart of FIG. 3. A passenger of a moving object operates theoperating unit 32 to select a desired facility so that a request forinformation regarding this facility can be made. The facility may be,for example, a parking lot or a restaurant, and the contents of theinformation regarding the parking lot may include the position, parkinglot capacity, and present vacancy status, and regarding the restaurantmay include the position, availability of parking, and type of cuisine.

As shown in FIG. 2, the information center 10 monitors whether or not arequest for information regarding a certain facility was made from theterminal 22 (S100). If there was an information request, a landmark on amap display in the periphery of the relevant facility is extracted fromthe map database 12 by the facility position information generator 18(S102). If the landmark on the map display has a linear form, such as aroad, railroad track, river, or coastline, and the facility located onone side of the linear landmark is displayed as being on the other side,the person receiving the information will misunderstand or becomeconfused. For example, if the landmark is a road and the facilitylocated on the right side of the road with respect to the direction oftravel is displayed as being on the left side, the person receiving theinformation will misunderstand the position of the relevant facility andmay not even be able to reach the facility.

The extraction of the peripheral landmark is described in FIG. 4. whichshows a peripheral map of a facility 50, for which there was aninformation request, on the map database 12 of the information center.In the periphery of the facility 50 positioned at point P₀ of longitudeX₀, latitude Y₀ are located two roads 54, 56 crossing at an intersection52. In the map database, the roads 54, 56 are each partitioned from theintersection 52 into two road links 54 a, 54 b and 56 a, 56 b. Extractedare two landmarks in the periphery of the facility 50 that connect toeach other, are positioned so as to sandwich the facility 50, and arepositioned the closest and the next closest to the facility 50. In theexample of FIG. 4, road links 54 b, 56 b connected at the intersection52 and positioned so as to sandwich the facility 50 from the top andbottom are extracted.

Furthermore, information regarding the facility position is generated(S104) at the facility position information generator 18. Thisinformation includes information indicating the relative positionalrelationship of the facility 50 with respect to the landmarks extractedin step S102, and more specifically, the position of point P₀ withrespect to points A and B, which are closest to point P₀ on theabove-mentioned landmarks 54 b, 56 b. Furthermore, the informationregarding the facility position includes the latitude and longitude ofpoint P₀.

As shown in FIG. 4(b), the information regarding the positions of theperipheral landmarks and the facility generated in step S102 and stepS104 is graphic information representing the shape of road links 54 b,56 b and the relative positional relationship of the facility with therelevant road links 54 b, 56 b. This information is then transmittedfrom the information center (S106).

The terminal 22 waits for and receives (S108) information regarding therequested facility, namely, information regarding the above-mentionedperipheral landmarks and facility position, transmitted from theinformation center 10. Then, based on the received latitude andlongitude information on the facility, facility position P₀′ (X₀, Y₀) onthe map database 24 of the terminal is determined (S110). This positionmay be a position differing from that in the map database 12 of theinformation center as shown in FIG. 4(c). Describing FIG. 4(c) indetail, roads 64, 66 correspond to the roads 54, 56 in the map database12 of the information center and intersect at an intersection 62. Theroads 64, 66 are further partitioned at the intersection 62 into roadlinks 64 a, 64 b and 66 a, 66 b. Longitude X₀ and latitude Y₀representing the position of the facility are directly shown on the mapdatabase of the terminal as position P₀′ With this facility position P₀′as a reference, the road links 54 b, 56 b extracted at the informationcenter exist at the positions shown as broken lines in FIG. 4(c).

The positions of the received landmarks and the landmarks in the mapdatabase in the terminal are then compared (S112). If they match (S114),a transformation matrix T is defined (S116) according to the followingformula. $T = \begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix}$

In this transformation matrix T, a coordinate transformation is actuallynot performed. On the other hand, as shown in FIG. 4(c), if thepositions of the received landmarks and the corresponding landmarks inthe map database of the terminal do not match and are shifted, atransformation matrix T for eliminating this shift is calculated (S118).Namely, as shown in FIG. 4(d), the transformation matrix T is determinedso that the received road links 54 b, 56 b match with the road links 64b, 66 b on the map of the terminal. This is achieved through known mapmatching methods and this operation is performed at the map matchingprocessor 34. The transformation matrix T is defined according to thefollowing formula.

T=T_(P)T_(R)

where $\begin{matrix}{T_{P} = \begin{bmatrix}a & 0 \\0 & b\end{bmatrix}} \\{T_{R} = \begin{bmatrix}{\cos \quad \theta} & {{- \sin}\quad \theta} \\{\sin \quad \theta} & {\cos \quad \theta}\end{bmatrix}}\end{matrix}$

Namely, the transformation matrix T is defined by parallel movements(T_(p)) for movements in the latitudinal and longitudinal directions (a,b) and a rotational movement (T_(R)) for movement through an angle θ.

This transformation matrix T enables facility position P₁ (X₁, Y₁) onthe map to be calculated (S120) in accordance with the following formulaby transforming facility position P₀′ (X₀, Y₀) in accordance with thereceived data.

P₁=TP₀′

The facility position P₁ on the map held in the terminal is thendisplayed on the display unit 30 (S122).

Thus, the present embodiment can prevent an improper display, such asthe display of the facility for which information was requested on theside opposite of its actual position with respect to a road or river.

In the present embodiment, the information regarding the peripherallandmarks to be transmitted from the information center 10 can includesuch information as route numbers of roads (for example national route1), width of roads, river names, and so forth. Thus, this map matchingoperation can be performed in a shorter time than when compared to theoperation for specifying by shape alone.

Furthermore, the information regarding the facility position to betransmitted from the information center 10 can be made to include onlythe relative position information with the peripheral landmarks withoutthe latitude and longitude information on the facility position. If theroute number or the like is specified as described above, landmarks forthe map matching can be narrowed down so that the operation need notrequire a considerable amount of time even though the latitude andlongitude are not specified.

The information regarding the facility position can also be made toinclude relative position information with the peripheral landmarks andthe address of the facility. A general position of the facility can bedetermined from the address of the facility, and a search can be made oflandmarks in its periphery having shapes matching the peripherallandmarks of the received information so as to also enable the facilityposition to be calculated.

FIGS. 5 and 6 are flowcharts showing one example of a method for theextraction of peripheral landmarks at the information center. Namely,one example of step S102 in the flowchart shown in FIG. 2 is shown indetail. Furthermore, in this method, at the information request from theterminal 22, information indicating the type of map database 24 held inthe relevant terminal is sent to the information center 10.

First, it is judged whether or not the terminal 22 is compatible withthe display of maps (residential maps) having sufficient detail topermit the position of an individual residence to be found (S200). Ifthe display is compatible with the residential map display, a search isset for roads having a width of 3 meters or more (S202), and if thedisplay is not compatible, the search is set for roads having a width of5 meters or more (S204). Among the roads to be searched, a terminal ofthe perpendicular line to the road link closest from the facilityposition is designated as point C (S206).

Next, it is judged whether or not the terminal 22 is compatible withmaps (VICS maps) specified by the VICS (Vehicle Information andCommunication System) Promotion Committee (S208). If compatible, thestarting point of the road link specified in the VICS map is set for thesearch (S210), and if not compatible, intersections of ordinaryprefectural roads or wider (roads classified to a certain level on upperlevels) are set for the search (S212). Among the starting points orintersections of road links for the search, the closest starting pointor intersection from the facility position is designated as point D(S214).

A route from point C to point D is then determined, and a sequence oflinks making up this route is designated from the link closest to pointC as link 1, link 2, . . . , link n (S216).

Since point D (endpoint of link n) is a point uniquely set regardless ofthe type of map database, the position of point C can be uniquely setfrom the route from point C to point D (link 1 to link n).

However, if all links (n links) making up this route are transmitted,the amount of transmission data may become large. The procedure givenhereinafter performs a reduction in the number of transmitted links.

Namely, a partial route comprising k items from link 1 (closest link topoint C) to link k (1 ≦ k ≦ n) is transmitted to the terminal 22. Thislink sequence is connected in a unique manner and has a minimum numberof links.

First, k=1, namely, the partial route comprising the closest link to thefacility position for which information is to be provided is selected(S218). Then, it is judged whether or not the number of links k of thepartial route has reached the number of links n of the entire route,namely, whether or not a partial route longer than the route from pointC to point D has been selected (S220). Then, it is judged whether or notthere is another link sequence equivalent in shape to the partial routehaving k number of links within a predetermined area (S222).

The area for which searching of the link sequence is performed can beset in the following manner. If the maximum value of error between mapdatabases is L, it is possible for point Q′, which is separated from thefacility position P by distance L as shown in FIG. 7, to be mistaken forthe point transmitted from the information center. From the viewpoint ofthe terminal, the actual facility position is within a circle centeringon point Q′ having a radius of L so that it is sufficient for theterminal to perform position correction within this range. From theviewpoint of the information center, the terminal searches for theactual position within a circle centering on point Q having a radius of2L. Thus, for a peripheral landmark to be extracted, namely, a partialroute 70, an area in which the circle having a radius of 2L is enlargedby a size of the partial route must not have a link sequence having thesame shape as the partial route 70. This area is denoted hereinafter asarea α.

Within this area α, if there is no other link sequence having anequivalent shape to the partial route of k number of links (S222), thispartial route is set as the peripheral landmark (S224). Otherwise, ifthere is a link sequence having the same shape as the partial routewithin area α, the link is extended by one toward point D in the routefrom point C to point D (S226). Therefore, the number of links k isupdated by the addition of 1 to the previous number of links. This isthen repeated until k reaches n (S220), and the partial route isextracted as the peripheral landmark when there are no more linksequences having the same shape.

Judging the type of links making up the partial route, such as the routenumber or name of the roads, and further the width of the roads, and notonly the shape of the link sequence making up the partial route, enablesthe peripheral landmark to be formed from a small number of links.

When searching the route from point C to point D, the peripherallandmark can be formed from a small number of links by increasing thenumber of left and right turns so that the changes in the shape and typeincrease.

Furthermore, in the above-mentioned embodiment, the facility positioninformation can be made to contain a map of the partial route 70, asshown in FIG. 8, from a predetermined reference point to the facility 50on which information is to be provided. The reference point can be setto the starting point of the VICS link or the intersection 52 ofordinary prefectural roads or wider as described above. A route 72 fromthe intersection 52 to the facility 50 can also be included in thefacility position information.

In the above-mentioned embodiment, the sending and receiving ofinformation between one terminal and the information center wasdescribed. A system need not be limited to this, and information may betransmitted unilaterally from the information center regardless of arequest from the terminal. Furthermore, in accordance with a requestfrom a terminal in a system, information may also be transmitted fromthe information center to another terminal.

Second Embodiment

General Configuration

FIG. 9 is a block diagram showing a configuration of the positioninformation provider system to which the second embodiment concerns. Avehicle 110 is provided with a navigation controller 112 for performingvarious types of data processing. To the navigation controller 112 isconnected a GPS device 114. The GPS device 114 detects the presentposition of the vehicle 110 by receiving radio waves from artificialsatellites. It is also preferable to use a DGPS (differential GPS)device for detecting the present position with greater accuracy byobtaining error information, such as from FM multiplexed broadcasts.

To the navigation controller 112 is connected a map database 116. Themap database 116, which may be based on CD-ROM, stores map informationof the entire country of Japan. In the present embodiment, the mapdatabase 116 stores relatively simple map information since informationis obtained from an external information center 130. To the navigationcontroller 112 is connected a display unit 118, which performs thedisplay of various types of information. To the display unit 118 isprovided a touch panel so as to allow various types of data inputs bytouching of the screen.

Furthermore, to the navigation controller 112 is connected acommunications unit 120. This communications unit 120 performs datatransmission and reception based on mobile communications, particularlywith the external information center 130.

The information center 130 includes a communications unit 132, whichperforms data transmission and reception based on mobile communicationswith the vehicle 110. The information center 130 further includes aprocessor 134 and a map database 136 to perform various types ofinformation provider services and the processing for these services. Inparticular, the map database 136 stores map data associated withcorresponding latitude and longitude based absolute position data. Inthe processor 134 is a transformer 134 a to serve as relative positionrelationship specifying means. The transformer 134 a transforms theabsolute value data that was read out from the map database 136 intorelative position data, which is a relative expression using closelinks. Therefore, the information center 130 can provide map data,expressed as both absolute position data and relative position data, tothe vehicle 110. Furthermore, the information center 130 is connected toother types of information centers by radio or wire so that traffic jaminformation, event information, and other information can be obtained.The map database 136 has extremely detailed data which is always kept upto date.

General Operation

It is assumed that a driver of the vehicle 110 in this sort of systemdesires to travel to a parking lot near a certain station. In this case,the relevant input is performed by an operation of the driver. From thetransmission command, the navigation controller 112 sends this requestvia the communications unit 120 to the information center 130. Theinformation center 130 selects an optimum parking lot by taking intoconsideration the local map database 136, the state of congestion of theparking lots, and so forth, and provides the position of the parking lotto the vehicle 110.

At this time, the processor 134 of the information center 130 transformsthe absolute position data of the parking lot obtained from the mapdatabase 136 into relative position data at the transformer 134 a. Forexample, if the position of the parking lot (point P) is near link i asshown in FIG. 10, point P is expressed from a relative position withlink i. Namely, as shown in FIG. 11, the link number of the close link,the distance from the starting point node of the link (terminal of thelink) to the closest point, and a vector (direction, distance) from thepoint are sent to the vehicle. A secondary mesh number indicates whichmap data, and the map data of the entire country, after being roughlypartitioned into a primary mesh, is partitioned into a secondary mesh.An ordinary map display is then performed using the map data insecondary mesh units. Specifying a mesh and then a link number enables apart of a road to be specified.

The navigation controller 112 of the vehicle 110 that received this sortof data reads out the corresponding map data from the local map database116 and displays it on the display unit 118, and based on the receiveddata, specifies the point P according to link i and displays it on themap. In this manner, since the point P is specified as a relationshipwith the link, the position of the point P will not end up on theopposite side of the road.

The map databases 116, 136 normally need only store absolute positionsas associated with coordinate positions on the map so that conventionalmaps can be utilized without change.

Processing for When a Link Cannot be Specified

Link i that was used in the data for point P sent from the informationcenter 130 may not exist in the vehicle 110. In this case, the vehicle110 notifies the information center 130 accordingly. This notice ofnonexistence becomes a retransmission request. The information center130 changes the rank of the link to be used and performs retransmission.

One example of the ranks of links is shown in FIG. 12. In this manner,each link is assigned a rank according to the type of road, such as rank1 for expressways, rank 2 for national highways, rank 3 for prefecturalroads or ordinary roads of width 13 m or wider, rank 4 for ordinaryroads of width 5.5 to 13 m, and rank 5 for ordinary roads of width 3 to5.5 m, and this is stored in the map database 136.

For example, the point P to be specified is at a position shown in FIG.13 with link A of rank 5 the closest, link B of rank 4 the next closest,and link C of rank 3 the next closest after link B. In this case, theinformation center 130 uses link A of rank 5 to specify point P andnotify the vehicle 110 of the position of point P. When a retransmissionrequest arrives, the rank is changed in sequence to a higher one inorder to use bigger links.

Namely, as shown in FIG. 14, the information center 130 first relativelyspecifies the position of point P from link A of rank 5 and transmits itto the vehicle 110 (Sll). Then, for a predetermined time, a check ismade for a response to the effect that the link A does not exist (S12).In S12, if a notice of nonexistence is received, the relative positionof point P is specified with a road one rank higher (link B of rank 4 inthis case) and transmitted (S13). If the result of S12 is YES, the rankis further raised and the relative position is transmitted.

In this manner, the notice of nonexistence is interpreted as aretransmission request, and retransmission is performed. During thisretransmission, a link having a high rank is used to specify therelative position. In the map database 116 of the vehicle 110, there isa high probability that the only data available concerns roads havinghigh ranks, and that roads having high ranks are assigned the same linknumber even in the map data of different sources. Raising the rank inthis manner raises the probability that a position will be specified bya relative position.

Furthermore, it is preferable to impose a fixed limitation on ranks sothat a rank is not changed to a higher one by 3 ranks or more, forexample. When this limitation is reached, the absolute position(latitude and longitude) is transmitted to the vehicle 110. Thisprevents unnecessary transmissions between the information center 130and the vehicle 110.

When the link used in the relative position specification does notexist, the link to be used at the vehicle 110 can also be specified.Namely, as shown in FIG. 15, the link closest to point P is first usedin the information center 130, and the position of point P is relativelyspecified and transmitted (S21) to the vehicle 110. At this time, theinformation center 130 also transmits the relative position (latitudeand longitude) of point P. If the relative position specification thatis received does not exist in the local map database 116, the vehicle110 searches for a link close to the position from the received absoluteposition. For example, perpendicular lines are drawn to each link fromthe received absolute position, and a link can be selected, such as by amethod selecting the smallest vector. The link in proximity istransmitted to the information center 130.

After the first transmission, the information center 130 waits for apredetermined time (S22) for another link to be transmitted. When thetransmission is received, the link is used to transmit the relativeposition of point P (S23). The link used in this case was specified atthe vehicle 110 and exists in the map database 116 of the vehicle 110.Therefore, the relative position data that was transmitted in S23 can berecognized at the vehicle 110.

Updating of the Map Database

As described above, if the link used in the relative positionspecification that was transmitted from the information center 130 doesnot exist in the map database 116 at the vehicle 110, the relativeposition specification is performed using another link. However, thefirst link used in the position specification of point P is optimum.Furthermore, to go to point P, it is preferable to pass the firstspecified link. Thus, it is preferable to provide data on a link thatdoes not exist in the map database 116 of the vehicle 110 in accordancewith a request from the vehicle 110 or a second transmission. Forexample, when the information center 130 provides the data shown in FIG.16 to the vehicle 110, and the vehicle 110 updates the map database 116according to this data, the relevant link can be displayed on thedisplay unit 118 in the vehicle 110. Namely, link data is transmittedcomprising secondary mesh code, link number, starting point node numberand coordinate, end point node number and coordinate, number ofcomplementary points, and coordinate for complementary point (repeatedonly for the number of complementary points). As a result, the relevantlink is defined by a line passing through the complementary points fromthe starting point to the end point. If this link is not the startingpoint for the link existing in the map database 16 of the vehicle 110,the data regarding these intermediate links is also transmitted.

In this manner, the map database 116 can be updated by the addition of anew link. This data may be deleted or kept after completion of the driveuntil point P.

If the starting point and end point of the link to be newly updatedexists on the link existing in the map database 116, a point specifiedfrom coordinates may shift from the existing link. In this case, it ispreferable to consider this shifted distance as an offset, as shown inFIG. 17, and to shift the entire new link by the amount of the offset.In this manner, taking the offset into consideration enables a correctpositional relationship to be maintained on the local map.

The link to be newly updated may be relatively specified using analready existing link. In this case, the starting point is specifiedwith a distance from the starting point of the already existing link,and the complementary points and end point are specified by a vectorfrom this starting point. In this manner, the data regarding the updatedlink is set as relative position data so that a correct positionalrelationship of the link and the peripheral condition is maintained, anddata is updated with a correct positional relationship.

Other

In the above-mentioned embodiment, relative position data was used whenproviding position data from the information center 130 to the vehicle110. However, when providing position data from the vehicle 110 to theinformation center 130, it is preferable also to use relative positiondata. For example, there are cases where it is preferable to specify thedestination with relative position data when the vehicle 110 sends arequest to the information center 130 for a route search to thedestination.

Namely, a map of the neighborhood of the destination is displayed on thedisplay unit 118 of the vehicle 110, and the destination is set byspecifying a point on this map. The absolute position (latitude andlongitude) of the destination is calculated from coordinate values onthe map. However, this absolute position is not necessarily correct. Onthe other hand, the relationship between the absolute position and theperipheral condition, such as of a road, is extremely accurate at theinformation center 130. When the absolute position incorporated at thevehicle 110 is recognized at the information center 130, the positionmay be on the opposite side of the road. Therefore, the final road tothe destination may indicate the opposite direction in the routeobtained from the route search.

Thus, it is preferable to provide at the navigation controller 112 ofthe vehicle 110 a transformer for transforming absolute position data torelative position data, and to provide the relative position data (orboth types of data) to the information center 130.

The vehicle 110 may provide position data, such as the present position,to the center or to other vehicles, and in this case, it is alsopreferable to use the relative position data.

What is claimed is:
 1. A position information provider system,connecting a terminal and an information center and in which theinformation center provides position information regarding a specificposition to the terminal, comprising: a center map database, whichstores a position regarding a linear landmark including at least a road;position information generating means for generating positioninformation that includes information regarding the landmark existing inperiphery of said specific position that is provided to said terminal,extracted from said center map database, and information regarding arelative position of the relevant position for the landmark in theperiphery of said specific position; and transmitting means fortransmitting said position information; said terminal comprising: aterminal map database in which information on the landmark on a linearmap display; receiving means for receiving information that saidinformation center transmitted; display position calculating means forcalculating a display position on a terminal map of said specificposition so that the position of said peripheral landmark that wasreceived on the basis of said received position information matches theposition of the landmark in the terminal map database corresponding tothe relevant peripheral landmark; and displaying means for displayingthe relevant specific position while superimposed on the map on thebasis on said calculated display position.
 2. The position informationprovider system according to claim 1 wherein: the information regardingsaid peripheral landmark includes shape and type of the relevantlandmark.
 3. The position information provider system according toclaims 1 or 2 wherein: said terminal transmits the type of terminal mapdatabase, which the relevant terminal holds, to the information center;and said position information generating means extracts said peripherallandmark according to the type of terminal map database that wasreceived and generates position information.
 4. The position informationprovider system according to claim 3 wherein: the peripheral landmark,which said position information generating means extracts, includes theroad in accordance with the type of terminal map database, which saidterminal holds; and furthermore the information regarding the specificposition includes a reference point that is set in advance on saidextracted road and detailed route information up to the specificposition of information to be provided.
 5. The position informationprovider system as in one of claims 1-4 wherein: the peripherallandmark, which said position information generating means extracts, istwo roads connected to each other and positioned so as to sandwich thespecific position of information to be provided.
 6. A positioninformation provider system in which terminal and information center areconnected by communications and the information center provides positioninformation to the terminal wherein the information center comprises:the center map database for storing the position of the road network aswell as connections of links, which are units forming the road network;and relative positional relationship specifying means for specifying anabsolute position with relative position data that represents a relativepositional relationship with a close link stored in the center mapdatabase; the terminal comprises: the terminal map database for storingthe position of road network and for storing the road network asconnections of links, which are units forming the road network; theinformation center transmits a provided specific position to theterminal as relative position data with said link; the terminal requestsretransmission when the link used by the received relative position datadoes not exist in the terminal map database; and the information centerretransmits the relative position data with another link close to thespecific position when the retransmission request is received.
 7. Theposition information provider system according to claim 6 wherein: saidcenter map database stores a rank for each link; and the informationcenter transmits relative position data using a link having a rankhigher than that of the link previously transmitted duringretransmission.
 8. The position information provider system according toclaim 7 wherein: said information center also transmits absoluteposition data of specific position while transmitting relative positiondata; said terminal specifies a link close to absolute position dataexisting in the terminal map database during retransmission request; andsaid information center transmits relative position data using aspecified link in the retransmission request.
 9. The positioninformation provider system according to claim 8 wherein: theinformation center transmits data on the shape of a link not existing inthe terminal map database to the terminal; and the terminal updates theterminal map database from the data on the shape of the link that wasreceived.
 10. The position information provider system according toclaim 9 wherein: the information center uses the data on the shape ofthe link to be transmitted as relative data using the link existing inthe terminal map database.
 11. The position information providerapparatus for transforming absolute position data into relative positiondata comprising: the map database for storing road network as coordinatevalues on map associated with absolute values; and transforming meansfor transforming an arbitrary absolute position into the relativeposition with the road network.
 12. The position information providerapparatus according to claim 11 wherein: relative position data to beprovided regards the position of a facility for which a request wasmade.